The golf balls generally include a spherical outer surface with a plurality of dimples formed thereon. The dimples on a golf ball improve the aerodynamic characteristics of a golf ball and, therefore, golf ball manufacturers have researched dimple patterns, shape, volume, and cross-section in order to improve the aerodynamic performance of a golf ball. Determining specific dimple arrangements and dimple shapes that result in an aerodynamic advantage requires an understanding of how a golf ball travels through air.
When a golf ball travels through the air, the air surrounding the ball has different velocities relative to the ball and, thus, different pressures. The air develops a thin boundary layer adjacent to the ball's outer surface. The air exerts maximum pressure at a stagnation point on the front of the ball. The air then flows around the surface of the ball with an increased velocity and reduced pressure. At some separation point, the air separates from the surface of the ball and generates a large turbulent flow area behind the ball. This flow area, which is called the wake, has low pressure. The difference between the high pressure in front of the ball and the low pressure behind the ball slows the ball down. This is the primary source of drag for golf balls.
The dimples on the golf ball cause a thin boundary layer of air adjacent to the ball's outer surface to flow in a turbulent manner. Thus, the thin boundary layer is called a turbulent boundary layer. The turbulence energizes the boundary layer and helps move the separation point further backward, so that the layer stays attached further along the ball's outer surface. As a result, there is a reduction in the area of the wake, an increase in the pressure behind the ball, and a substantial reduction in drag. It is the circumference portion of each dimple, where the dimple wall drops away from the outer surface of the ball, which actually creates the turbulence in the boundary layer.
Lift is an upward force on the ball that is created by a difference in pressure between the top of the ball and the bottom of the ball. This difference in pressure is created by a warp in the airflow that results from the ball's backspin. Due to the backspin, the top of the ball moves with the airflow, which delays the air separation point to a location further backward. Conversely, the bottom of the ball moves against the airflow, which moves the separation point forward. This asymmetrical separation creates an arch in the flow pattern that requires the air that flows over the top of the ball to move faster than the air that flows along the bottom of the ball. As a result, the air above the ball is at a lower pressure than the air underneath the ball. This pressure difference results in the overall force, called lift, which is exerted upwardly on the ball. Golf ball dimples having a conventional circular shape have been demonstrated through decades of use to produce aerodynamic characteristics that are as good as or better than other shapes such as polygons. This is believed to result from the radial symmetry of a circle, which presents the same geometric shape to the airflow regardless of the incoming direction, as well as the fact that circles don't have corners to cause airflow disruptions.
A disadvantage of circular dimples is that they cannot be tessellated or tiled on the surface of a ball with narrow uniform gaps. Even with ideal packing, there will still remain triangular pieces of land area where three dimples come together. Among other things, this causes inconsistent turning angles of the airflow entering the dimples. For example, as shown in FIG. 1A, air that is traveling across a piece of land before entering a dimple will encounter a turn angle approximately equal to the dimple's edge angle. On the other hand, as shown in FIG. 1B, at a point where two dimples touch or nearly touch, the air will be rising out of one dimple and turning directly down into the other, resulting in a turn angle of approximately twice the dimples' edge angle. Since turn angle affects the character of the flow, especially in terms of boundary layer separation and turbulence generation, both critical for golf balls, this situation is less than optimal since both conditions cannot be made ideal at the same time.
Based on the significant role that dimples play in golf ball design, manufacturers continually seek to develop novel dimple patterns, sizes, shapes, volumes, cross-sections, etc. Thus, there exists a need for an improved dimple configuration that provides more optimal airflow conditions.